Year	% of total
1970	74.64750928407372
1971	75.1861999873268
1972	74.40698242004473
1973	73.1433365414334
1974	73.29924469386894
1975	72.63471477400788
1976	73.290058204259
1977	72.41497118052621
1978	70.95974426651026
1979	71.61940153174395
1980	71.78108438742463
1981	72.07229617635738
1982	72.46012257986789
1983	71.98700562077516
1984	72.91182422106193
1985	72.64746416635154
1986	72.29502038817427
1987	73.62582292180873
1988	74.47744735888064
1989	74.77110285479604
1990	81.07157699562035
1991	81.23415840035048
1992	81.29810948950058
1993	80.49901718343796
1994	81.05048537780347
1995	82.38307049467583
1996	82.68270540172492
1997	80.47576423359644
1998	80.05404402998913
1999	80.03860219423
2000	78.78418980522171
2001	78.12644802553673
2002	78.32648137662785
2003	77.6488482201997
2004	77.59379535127162
2005	77.28515031885819
2006	76.066840968512
2007	74.73240567299973
2008	73.85261797026503